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DeoxyInosine: Don’t call me a universal base!

DeoxyInosine, a naturally occurring base, was considered the first “universal” base—meaning that it could base pair with the other natural bases, A, C, G, and T. However, this terminology has encountered some criticism, notably from Michael Smith, winner of the Nobel Prize for Chemistry in 1993 for developing site-directed mutagenesis, who mentioned deoxyInosine in his Nobel Prize acceptance speech [1]: “I have always been puzzled by the widespread acceptance of the idea that deoxyInosine is precocious in base pairing because Inosine behaves in a precocious manner in t-RNA duplex interactions. Studies on deoxyInosine, in fact, indicate that it functions as a specific analog of deoxyGuanosine, although it does not self-aggregate as does deoxyGuanosine.” Subsequent studies have shown that Dr Smith was correct: deoxyInosine binds preferably to dC [2]. So go ahead and use it in experiments, just don’t call it universal!


  1. www.nobelprize.org
  2. Watkins Jr NE, SantaLucia Jr, J (2005) Nearest-neighbor thermodynamics of deoxyinosine pairs in DNA duplexes. Nucl Acids Res 33(19):6258–6267.

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Author: Martin Whitman is a Technical Support Representative at IDT.

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